Research is planned which will define the mechanisms involved in the regulation of synthesis of fatty acid synthetase in rat liver at the molecular level. We will purify and characterize the mRNA coding for this enzyme and use it to prepare a complementary DNA copy. By the use of in vitro translation and cDNA-RNA hybridization, the amounts of mRNA for fatty acid synthetase present in livers of rats under different dietary and hormonal states will be determined. These will include fat-free and polyunsaturated fat feeding, treatment with several hormones known to affect the rate of fatty acid synthetase synthesis, and experimentally induced diabetes. By careful analysis of the products of translation of fatty acid synthetase mRNA, we hope to be able to better define the structure of the enzyme complex. Cultures of isolated rat hepatocytes will be used to study the regulation of fatty acid synthetase in vitro. By maintaining these cells in culture, various effectors can be added to the medium and the rates of synthesis and degradation of the enzyme measured under controlled conditions. With this system, we hope to better define the events which lead to regulation of the levels of fatty acid synthetase in the intact animal.